1. Field of the Invention
This invention relates to a method, device, and system for rapidly inducing protective levels of hypothermia in the brain and the body.
2. Description of Prior Art
Patients suffering from stroke, cardiac arrest, or head trauma, or have undergone invasive brain or vascular surgery are at risk from secondary ischemic brain injury. Secondary ischemic brain injury is a result of the innate healing response of the brain to the original insult caused by several not completely understood mechanisms. Regardless of the specific mechanisms involved, the end result is swelling of the brain caused by edema, which can lead to a critical or terminal rise in intra-cranial pressure, or cell death and loss of brain function.
Patients suffering heart attack often suffer damage to their heart due to secondary injury caused by ischemia. Ischemic damage to the heart is the main cause of death and disability following heart attack.
It has long been known that hypothermia is neuroprotective. Hypothermia has a positive affect on all know mechanisms that lead to secondary brain injury. Hypothermia is routinely used during brain and other invasive surgeries to protect the brain from surgical interruptions in blood flow. Hypothermia has also been shown to be effective in controlling swelling of the brain in trauma and stroke patients.
It has been more recently discovered the hypothermia is effective at protecting the heart from secondary ischemic injury due to heart attack.
The effectiveness of hypothermia is a function of depth, duration, and the amount of time that elapses between the original insult and achievement of protective levels of hypothermia; the earlier, deeper (within a range of 30° C. and 35° C.), and/or the longer hypothermia is applied the more protective it is. However, hypothermia has historically been applied systemically, and the depth and duration of hypothermia is limited by the patient's ability to tolerate the therapy.
Systemic hypothermia has historically been accomplished by immersion of the patient's body in a cool bath. Today there are several commercial systemic hypothermia systems available. They consist of blankets or pads where cooled water is circulated through channels in the walls of the blanket or pad, and the patient's body is maintained in intimate contact. Medivan Corp. manufactures an example of a modern hypothermia system under the trade name Arctic Sun Cooling System.
Systemic hypothermia has been demonstrated to be effective in reducing secondary injury from stroke, trauma, and surgery however, there are several drawbacks to this approach: 1) It may take several hours to lower a patient's body to therapeutic temperatures. This delay in achieving therapeutic temperatures allows for the progression of irreversible secondary injury to the brain and heart. 2) Hypothermia cannot be initiated until after the patient has been admitted to the hospital. 3) The entire patient's body is cooled in a slow and uniform manner; protective levels of hypothermia in the brain is not achieved until the whole body reaches protective levels of hypothermia.
Attempts have been made to induce hypothermia by cooling the surface of the head. A company, Flexoversal from Hiden, Germany manufactures a head cooling device under the trade name of “Hypotherm Gel Cap” This device is a head cap with a gel substance within its walls. The “Gel Cap” is placed into a freezer prior to use, then is fitted to the head of a patient. The gel within the walls of the cap absorbs heat from the head. Also, described in the art are cooling caps that have cold fluid circulating through the walls of the cap to absorb heat from the head. Reports from clinical trials using such devices have been disappointing in that they have not been effective in inducing hypothermia in patients. Although, theoretically these devises should be capable in inducing hypothermia, there are several practical limitations in design of the devices, and in the way they are used that limits effectiveness. A significant problem is that hair; especially dry hair is a very effective insulator. There is significant variation from patient to patient in the thickness of hair on the head, and its distribution. A device that does not address the insulating effect of hair, and its variability among patients is will ineffective in inducing hypothermia in a consistent manner. A second significant problem with head cooling described in the art is that the cooling medium (gel, or circulating water) is separated from the head by the material that the device is made of. Most devices described in the art are made of plastic or woven material, both of which are highly insulative and greatly reduce the amount of heat that is transferred from the head into the cooling medium.
Nowhere in the art is it suggested that directing evenly distributed jets of saline at near 0° C. at the scalp in a vigorous manner will effectively and consistently induce hypothermia regardless of the amount of hair on the head, or its distribution on the head. Nowhere described in the art is a means of directing evenly distributed jets of saline at the scalp and a means of scavenging the saline for reuse in a closed loop system. Nowhere described in the art is a system consisting of: a small portable console, and a head cooling device, where the head cooling device is connected to the console by an umbilical, where the head cooling device and console work in a continuous operational relationship with each other to direct jets of saline at near 0° C. in an evenly distributed manner at the scalp, to then scavenge the expended saline from the vicinity of the head and return the expended saline to the console where the saline is then cooled to near 0° C. and where the saline is then returned to the head cooling device where it is once again directed at the scalp.